1. Field of the Invention
The present invention relates to a technique for detecting degradation in an integrated circuit chip.
2. Related Art
Electromigration is a physical process that occurs when a flow of electrons through a metal causes the metal atoms to move. For example, the flow of electrons can cause metal atoms in the leads of an integrated circuit (IC) chip to migrate through the molding resin compound used in the IC chip package. The migrating metal atoms can eventually produce an electrical short-circuit pathway between the leads which can cause the IC chip to fail. Note that the electromigration process can be accelerated by: temperature, temperature cycling, voltage differences between adjacent leads, and the presence of contaminants that can make the molding resin act as an electrolyte
Electromigration poses two problems: (1) the symptoms associated with electromigration failures in IC chips are difficult to detect; and (2) a high level of “No Trouble Found” (NTF) mis-diagnoses can occur, which can be a substantial warranty cost to vendors and a significant factor for customer dissatisfaction. Electromigration-related failures can lead to high levels of NTF mis-diagnoses because the initial electrical short-circuit pathway between leads can carry enough current so that the pathway fuses (i.e., becomes an open circuit, wherein the pin-to-pin resistance returns to a high value). Hence, when the degraded IC chip is analyzed in the lab, the IC chip appears to be functioning properly even though degradation due to electromigration is present.
The only unambiguous technique for determining whether electromigration is the cause of failure in an IC chip involves performing a high-resolution X-ray analysis that can identify electromigration pathways inside the IC chip. Unfortunately, this process is costly, destructive to the IC chip, and resource-intensive.
Hence, what is needed is a method and an apparatus for detecting degradation in an integrated circuit chip without the problems described above.